1. Field of the Invention
The present invention relates to the technical field of umbrella for shading from sunlight and rain, and in particular to the technical field of large-sized beach umbrella.
2. The Related Arts
Umbrellas that are used as sunshade or rainshade are generally classified as two types, of which one is portable, while the other if fixed. The portable umbrellas are designed for the consideration of easy carrying so that they have a small size and light structure. On the other hand, the fixed umbrellas, such as beach umbrella and advertisement umbrella, which are both of large-sized umbrellas, often have a large size and heavy. The large-sized umbrellas are generally fixed outdoors for shading from sunlight or rain. The fixed umbrellas are often designed to allow of expansion and collapse for the purposes of easy storage, protection of the umbrellas against aging or deterioration caused by intense sun light, and protection against caused by gusts in the nighttime. Due to the large size and heavy weight, it takes a great effort in carrying out the expansion or collapse operation of the umbrellas. Further, in the operation of expansion or collapse, since the fixed large-sized umbrellas often have a runner that must be moved for a long stroke, for a short person, he or she needs a stool to stand thereon in order to move the runner to a predetermined height and secured in position to a central post in expanding the umbrella. This is effort consuming and difficult.
Known references, such as U.S. Pat. No. 5,361,792, disclose a self-opening umbrella that is operated by pushbutton based control means and such a known umbrella achieves the self-opening operation through a complicated control arrangement that includes a runner that is movable along a central shaft, an intermediate collar that is fixed to an upper end of the central shaft, and a cap that is fixed to the upper end of the central shaft. However, the disclosure of the known reference shows that such an arrangement is composed of a great number of parts and has an extremely complicated structure, making an umbrella incorporating such an arrangement very heavy and thus only fit for small-sized portable umbrellas and not applicable to the large-sized umbrellas discussed above.